If you want to go back to where it all started then I think you’re probably going to have to go back to the French slave owners in Louisiana, who for their own delectation taught their slaves how to play (orchestral) musical instruments.

as Lennon said before Elvis there was nothing so unless you want to listen to early blues i would not bother tbh

Well, considering Elvis was influenced a lot by the country swing that was all over the radio, you could do worse than check out people like Hank Williams.
Lennon could, and did, talk utter bollocks, and this statement is a clear example.

Willie Dixon “influenced” led Zeppelin quite a bit.
Lightning Hopkins, blind lemon jefferson, Elmore James also worth listening too.
Son House is pretty good too, though he sounds a bit pissed in this version
[video]http://m.youtube.com/#/watch?v=QwjGytOVVQA[/video]

“He was the first person we had heard of from Britain to get to the coveted No. 1 in the charts, and we studied his records avidly. We all bought guitars to be in a skiffle group. He was the man.” — Paul McCartney
“I wanted to be Elvis Presley when I grew up, I knew that. But the man who really made me feel like I could actually go out and do it was a chap by the name of Lonnie Donegan.” — Roger Daltrey

There are the old blues like Robert Johnsone, Muddy and Howling wolf were later [ 60s ] , or theres jazz like Jelly Roll Morton ,Jug bands or you could listen top the people that Elvis copied like Big Joe Turner .
If you go down the blues root Lightning Hopkins is good , or Sleepy John Estes ,Son House or Leadbelly .And no they don’t all sound the same , there’s a rich variety .